I don't know if you are a church goer, but there is a church which meets in the centre of Heraklion close to the McDonalds takeaway restaurant. Sunday meetings commence at 10.30am. Worship is contemporary in style and meetings are conducted in both Greek and English.http://christiansincrete.org/churches/evangelical-church-heraklion/
My wife and I live in the west of the island and have been attending a church in Tavronitis. It is a great place to meet and make new friends.
However you cannot ignore the need to try to make friends in your immediate neighbourhood. More and more tavernas and kafeneons are seen with couples and families. If you find one in which you feel at home you will soon find others who are like minded, both local and ex-pats.
Hope you settle soon and I'm sure that once the school starts you will meet many other mums in your situation